(1) Any suit to recover any tax authorized or imposed by this Title, other than real estate taxes, personal property taxes not imposed under § 19-1102, and General Business Taxes, shall be begun within 6 years after such tax is due or within 6 years after a return or a report has been filed, whichever date is later; but this limitation shall not apply in the following cases;^[88]

(a) where the taxpayer has failed to file the return or report required under the provisions of this Title;

(b) where an examination of a return or report filed by the taxpayer and of other evidence relating to such return or report in the possession of the Revenue Commissioner reveals a fraudulent evasion of taxes, including, but not limited to, substantial understatement of gross income, net profits, gross receipts, or any other receipt of income, moneys or funds in any such return or report;

(c) where the taxpayer has collected or withheld tax funds or moneys of any nature or description under this Title as agent of or trustee for the City or the School District of Philadelphia, and has failed, neglected or refused to pay the amount so collected or so withheld to the City or the School District of Philadelphia.

(2) All defenses to the collection of any tax authorized or imposed by this Title shall be raised by appropriate petition pursuant to Chapter 19-1700.^[89]

(3) Where a taxpayer has filed any petition pursuant to Chapter 19-1700, the period of limitation set forth in § 19-509(1) shall be tolled until final determination of such petition has been made.